Property development during film formation of two component waterborne polyurethane using dielectric spectroscopy

A dynamic dielectric analysis (DEA), coupled with infrared spectroscopy (IR), Persoz hardness and dynamic mechanical analysis (DMA) were used to correlate the film formation, curing, and final property development of a two component (2K) waterborne urethane coating. The 2K waterborne urethane coating is based on Air Products' novel zero volatile organic compound (VOC) Adura [trademark] polyol technology. The coating is cured at ambient temperature. The change in capacitance and resistance (which is directly proportional to ionic viscosity before gelation) was studied using DEA. The water evaporation, the consumption of isocyanate groups and appearance of urethane and urea groups were monitored by IR. The hardness development and final Tg of the coating under various conditions were studied by Pendulum Persoz hardness tester and DMA. A correlation among those observations was attempted, and the curing and film formation process of this system is rationalized based on the experimental data.